1. Field of the Invention
The present invention relates generally to transceivers and more particularly to wireless cable transceivers.
2. Description of the Related Art
FIG. 1 illustrates signal bands that are associated with a variety of communication services that deliver communication signals to consumers. In the oldest of these communication services, off-air television and frequency modulation signals are received through a consumer antenna. Off-air television channels are arranged in three different signal bands that are included in a frequency span of 54-800 MHz and off-air frequency modulation signals extend across a signal band of 88-108 MHz. Subsequently, consumers were offered the alternative of cable television (CATV) in which hard cables deliver television and frequency modulation signals to consumer dwellings over a CATV signal band of 54-648 MHz. Off-air and CATV communication signals are, therefore, substantially contained within a consumer signal band 10 of FIG. 1 that spans 5-750 MHz.
Consumers can presently choose between an additional pair of communication services. In a first one of these services, communication signals are provided by a direct broadcast satellite (DBS) system. In this system, satellites radiate microwave signal beams in C-band frequencies (e.g., 3.7-4.2 GHz) and Ku-band frequencies (e.g., 11.7-12.75 GHz). Upon direct receipt at a consumer antenna, these satellite signals are initially downconverted to a signal band of 950-1450 MHz before further downconversion and detection at either 479 MHz or 70 MHz.
In a second one of these services, communication signals are provided by a wireless cable system in which signals are directed from a service provider's antenna to a plurality of subscriber antennas. The signals can be sent over two different wireless cable signal bands. One band is the multipoint distribution service (MDS) frequency band 11 of FIG. 1 that spans 2150-2162 MHz. The other band is the multichannel multipoint distribution service (MMDS) frequency band 12 that extends across 2500-2686 MHz. Signals in these wireless cable bands are typically downconverted at subscriber dwellings by low noise block downconverters (LNB's) that use a converter signal 13 at 2278 MHZ to form MDS and MMDS intermediate frequency bands 14 and 15 that respectively span 116-128 MHz and 222-408 MHz.
The communication signals provided by these consumer services were initially limited to television and frequency modulation signals. Consumers are now being offered, however, an increasing list of other communication options. For example, a communication service can operate as an internet service provider (ISP) who provides access to the internet. It was also initially envisioned that signals were only downlinked to consumers but some of these communication services have now become two-way streets in which consumers uplink data signals (e.g., signals associated with the activities of pay-for-view, banking, home shopping, medical alarm and fire/security).
In the past, uplink data from consumers has typically been channeled over telephone lines. As a first example, consumers communicate home shopping selections over their telephones to wireless cable providers. As a second example, consumer computers communicate through modems and telephone lines with internet ISP's. Telephone lines and conventional modems, however, form a speed bottleneck in these data communications because of their low transmission rates (typically less than 56 kbps).
To provide a path around this bottleneck, the signal band 10 of FIG. 1 is now generally divided into an uplink signal band 16 of 5-65 MHz for consumer uplinking of data signals and a downlink signal band 17 of 50-750 MHz for provider downlinking of communication signals. Recently introduced data interface modules (e.g., cable modems) take advantage of the higher uplink bandwidth. Accordingly, these modules have significantly higher data transmission rates (e.g., 500 kbps-3 Mbps).
The provider antenna-subscriber antenna structure of wireless cable is especially suited for two-way signal flow. As stated previously, communication signals from wireless cable headends are typically downconverted at subscriber dwellings by LNB's and subscriber data is presently communicated back to the headend by telephone lines which have the speed limitation referred to above. This data path limitation could be removed by provision of a high-speed uplink path. In anticipation of this, a pair of data-uplink signal bands have been proposed. One is a limited-bandwidth (2686.0625-2689.8125 MHz) instructional television fixed service (ITFS) signal band and the other is a wider-bandwidth (2305-2360 MHz) wireless communication service (WCS) signal band. These are respectively shown in FIG. 1 as signal bands 18A and 18B.
In an exemplary uplink path proposed in U.S. Pat. No. 5,437,052 (issued Jul. 25, 1995 to Hemmie, et al.), a bi-directional converter has a downconverter for downconverting MMDS programming signals (i.e., signals in the MMDS band 13 of FIG. 1) to converted signals in the 222-408 MHz range (i.e., intermediate frequency band 16 in FIG. 1) and an upconverter that converts data/information signals in the 116-128 MHz range (i.e., intermediate frequency band 15 in FIG. 1) to the MDS signal band (i.e., MDS band 12 in FIG. 1).
This proposed uplink path, however, ignores a frequency gap 19 between the uplink signal band 16 and the intermediate frequency MDS band 14 of FIG. 1. Subscribers wishing to access this uplink path with data interface modules that operate in the uplink signal band 16, would have to purchase additional interface modules that could span the frequency gap 19. In addition, if this upconversion structure is used to communicate data to the MDS band (11 in FIG. 1), it will invert the data's frequency order in contrast to the conventional MMDS downconversion process which does not invert frequency order. This inversion typically creates problems in communication and data transfer systems.